Figure 119

Thyroid Factor

The Natural Thyroid Diet

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Diagnostic criteria for the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Clinically, SIADH is characterized by a decrease in the effective extracellular fluid osmolality, with inappropriately concentrated urine. Patients with SIADH are clinically euvolemic and are consuming normal amounts of sodium and water (H2O). They have elevated urinary sodium excretion. In the evaluation of these patients, it is important to exclude adrenal, thyroid, pituitary, and renal disease and diuretic use. Patients with clinically suspected SIADH can be tested with a water load. Upon administration of 20 mL/kg of H2O, patients with SIADH are unable to excrete 90% of the H2O load and are unable to dilute their urine to an osmolality less than 100 mOsm/kg [15]. (Modified from Verbalis [15]; with permission.)


Decreased extracellular fluid effective osmolality (< 270 mOsm/kg H2O)

Inappropriate urinary concentration (> 100 mOsm/kg H2O)

Clinical euvolemia

Elevated urinary sodium concentration (U[Na]), with normal salt and H2O intake

Absence of adrenal, thyroid, pituitary, or renal insufficiency or diuretic use


Abnormal H2O load test (inability to excrete at least 90% of a 20-mL/kg H2O load in 4 hrs or failure to dilute urinary osmolality to < 100 mOsm/kg)

Plasma antidiuretic hormone level inappropriately elevated relative to plasma osmolality

No significant correction of plasma sodium with volume expansion, but improvement after fluid restriction

Central Nervous System

Gastrointestinal System







Lethargy Moderate Agitation Ataxia

Musculoskeletal System


Diminished deep tendon reflexes


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